Synchronous motor demonstrator



4 Sheets-Sheet 1 oooooooooooaoo o oo o o o.

o a o ooo oooooooo nooo o a H. M. TUCKER DQOOOOO OUT 0F PHQSE EMF 90PHHSE l LERONG o o oo SYNCHRONOUS MOTOR DEMONSTRATOR` Filed April 4,1.949

o n 0 o0 M 000600000000 O July 18, 1950 JNVENTOR. #UQ/@VM 75655@ BY,977' an i /ME/vf- H. M. TUCKER SYNCHRONOUS MOTOR DEMONSTRATOR July 18,19.50

4 Sheets-Sheet 2 Filed April 4, 1949 INVENTOR Aro/l 4g maf #6E/Vr- July18, 1950 H. M. TUCKER sYNcHRoNous MOTOR' DEMoNsTRAToR 4 Sheets-Sheet 3Filed April 4, 1949 INVENTOR.

' A//Zy /m TUCKEE E n i f E X g l e 5 i-aff 5- i Ql I I I l l July 18,1950 H. M. TUCKER '2,515,278

sYNcHRoNoUs MOTOR DEMoNsTRAToR v Filed April 4, 1949 4 sheets-sheet 4 inINVENTOR. 2 //Z/QJ/ Af. aa/fe Patented July 18, 1950 SYNCHRONOUS MOTORDEMONSTRATOR Harry M. Tucker, Dayton, Ohio Application April 4, 1949,Serial No. 85,401

(Granted under the act of March 3, 188s, as

. amended April 30, 1928;` 370 O. G. 757) Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes without payment to me of anyroyalty thereon.

This invention relates to training apparatus and particularly to thevisual type of training aid which may be used in` instructing a largeclass. y

It is the object of the invention to provide a training aid for clearlyand simply demonstrating the theory of operation of a synchronous motor.l

Briey, in accordance with the invention, apparatus is provided forillustrating (1) the voltage waves and the phase relation therebetweenapplied to a synchronous motor and (2) the flux distribution in asynchronous motor at various points of the applied voltage waves. Thevoltage waves are portrayed by transparent traces on an opaque plate orpanel With a light source` and an interposed movable masking devicelocated behind the `panel so that the variations of the waves withrespect to time are illustrated. The flux distribution in the motor isillustrated by means of a disc of opaque material in which thecross-sectional area of the core and associated salient poles of thestator, in a plane perpendicular to the shaft, is perforated to permitthe passage of light. Each of the sectoral areas of the disc betweenadjacent poles is illuminated from the rear by a separate controllablelight sour-ce and cam operated shutters are interposed between theperforated poles and the light sources. A statorof transparent materialconformingy to the `cross-sectional area perpendicular to the shaft ofthe core and associated poles is placed over the perforations in thedisc and a rotor of transparentmaterial'is arranged to rotate in thespace between the poles to simulate the rotor of a synchronous motor. Byproperly coordinatingthe position of therotor with the action of theshutters, the lswitching of the lights behind thesectoral areas of the`disc and the position of the above mentioned movable mask used inconjunction with the voltage wave representing apparatus, the lightpassing through the perforated areas is made to represent the fluxIdistribution in asynchronous motor for various points on the voltagewaves and various positions of the rotor.

The details of a preferred embodiment of the invention are-shown in theaccompanying drawings in which:

Fig.y 1 shows the front panel of the demonstrator ,as seen by thestudent.

` by the ilux indicating device at various points of the voltage waves.

Referring to Fig. 1 the front panel I of the demonstrator contains thevoltage wave indicator generally referred to by reference numeral 2 andthe flux indicator generally referred to by reference numeral 3. In theembodiment shown the panel I is made of a clear transparent syntheticresin coated on the back surfaceV with a black opaque paint with thepaint removed wherever'it is desired for light to pass through thepanel. In this Way 'twosine waves 90 apart in phase are represented inthe voltage wave indicator 2 by removing the paint at'successive small gcircular areas along the waves. In a similar Way the zero axis 6 andvertical lines 'I are delineated on the panel I. The lines ,'I arelocated 45 electrical degrees apart so that one complete cycle of eachof waves 4 and'5` is shown. Transparent circular areas 8 through IB arepositioned below lines 1 and are backed by lights 8 through LIB' (Fig.2) respectively which shine through these areas to indicate variouspoints on the voltage waves, as will be seen later. Various legends. onthe panel I, such as Il and I8, are formedvby removing the opaque paintand applying .the desired lettering in the transparent areas. Inconnection with ux indicator 3 the circuits connecting each of thevoltages shown in the wave indicator 2 to the armature windings oi themotor are shown in dotted outlines I9 and 26 formed by removal of smallcircular areas of paint at regular intervals along the conductors as inthe case of waves 4 and 5 and lines 6 and 'I of wave indicator 2. Means,not shown, are located behind panel I for continuously illuminating thetransparent areas of the legends and the circuits I9 and 20.

The wave indicator 2 is shownV more completely in Fig. 2. Positioneddirectly back of plate I, but shown displaced therefrom in the figurefor the sake of clarity, is a reflector having back2I, sides 22 and 23and bottom 24. The height and length ofL the reflector is suiiicient tojust cover the area of plate I occupied by waves 4 of the belt isperforated and these perforations engage teeth on drum 3|soi-that-arvxedref lationship exists between the belt and the angularposition of shaft 32 on which cylinder 3`|-ismounted. The diameter ofcylinder y3+ -isnsuch-` that the belt 21 moves a distance equal to one4fourfrstrips'of; perfor-ations 48, 49, 5|) and 5|l of wavelength ofwaves 4 and v5 on panel I'dur-ing one revolution of shaft 32. `Asanopaque ,por-

tion of belt 21 moves from le'ft'y torightuneov'er-T ing the reflectorthe Waves 4 'and 5 are progressively illuminated from left to right.When full illumination/of'waves4'andj`5 is'gobt'ained the next opaquesectionfbgifns,tomoveacross the reflector Iprogressively *darkening the'Waves `from left to right. As the resultrof tlf`1is-process com'-plete' cycles ofea-ch of waves'A 4`fan'df5iappear'to the"obser`ver"to-'move from"le'ft to` right across thep'aneP |'.f 'Thecommutator'SS the'detail'sfof Which-'- are shown in Fig," 5;'is'idriv'en" by-shaftz and, as one of its functions,'operates'to'momentarilyenergizeeach of lights -flthrouglr l 6 'when a@dividingflineL between a clear" and larropaque section of belt 21 passesa corresponding verticaljline 1; Vihen'jbeltl 21 is in motion'the'holesthrough* the *center thereofL register -periodically with theholesin-fzero reference line E' sothatthe locationI Yofthe line'isalways apparent* even "when thereflector is vcovered by an opaqueporti'on'oi tnefbeit. i

Asi-seenl above; the wavendicator Z'portraysa two-phaseryoltage Viniwhich the' phases* are f90 electrical wdegrees apart. fThevfluxindfcator 3,' shown in Figs'.l 1' and 3'isin" the forrriV ofasimple two-golflasesynchronous motor"designedy to operate` with a;two-phase"voltage" of' 'the type portr'ayed'.v The stator'ora'rmature'core for themetoris'. represented by 'a rin-g "420" 'of clear'l plastichavingsalientl poles 4 j 42j L'Imanol 44j; i' Thepha'se I winding is gmountedon,y poles '41 "andj' 43an'df the phase-2'A winding'on'poles, 42''and'lli these'widings` beingv illustrated by"etch i`ng on thecl'earplastic: 'Y Since the' space s'ep'arationof thesettvz') windingsisjthesarne "as" the electricalseparation o-'the voltages appliedthereto,Y namely 90; "the uxesrproduc'edby theA two'` windings'combine't'o produce a rotating twoj-pole magr"ieticfield; i' The speedvofrotation'of this eld'is revolutions perY ninute'where f'i'si thefrequency of the two-phase Lvoltagesd andA 1r is the number ofpoles'ainthe'resultantffleld For 'Fzffiv C; P. S; the speed 'would be 2y l @.3600 R. P.' M. It is vof course intended'thatthe demonstratoroperate at a much lower' speed to permitv observation. Y

The rotor or.'- fi'eld vcore"y 45. is.'Y made of f the samel clear.plastic materialasfthe stator and-hast two "salient polesmarked: Nf' andiSf'whicli,u i in-` anl actual motorl of this type, align-:with theLtwopolesiY of. the yro'catingffleld; andi lmove therewithso thatthef rotorrevolves at thei speedv of; the.

4 field, usually referred to as synchronous speed. The rotor elds ofsynchronous motors are usually energized by direct current and toillustrate this the letters DC are also etched on the clear plastic.Provision is made for mounting the rotor on the end of shaft 4E. Thetransparent stator 240iand irotor 45 are backed'loyl ay disc-"41 ofopaque material such as metal. The area of plate 41 located under theouter ring of stator 40 is perforated, and also about the same width asand centered on poles '442,142yf43andi44, extend radially toward thecentei'roffdisc-.Mrv .Positioned directly behind strips iB-5| areshutters 52-55, respectively, each perforate'dl'l in the same pattern asthe perforated strips. The shutters. are actuated in a radial di-`rec'tionlbycam56mounted on shaft 45. When the 'shutters are on thejhigh portion of the cam the perforations thereinrregister with thecorresponding perforations in d-isc-41VVV topermit the passage oflight,andwhen"on the --low portion of' the cam the'- perforationsare 'out-of#register and the passage of light is-blocked: The shutters' are-kept-inengagementuwith' the-v cam by meansof an annular spring 51 whichengages a small postA (notshowni extending-rearward1-y from eachshutter. The shutters are keptin alignment byguides-onthely back ofdiscflll` as shown'- at58 Y The design of 'thecam-isfshown i'n-Figz 4;thev cam being drawn to a larger scale in this figure. The lrotorwtiiiismountedv onA shaft '46 -w-ith'its polar axis in alignment vwith thea-xis `Qi-'ofthe cam as'shown inIFig'; 4; -The design is vsuchlthatshutters 52 and'5'4are--open-andshutters 53 and 55* closed when' the'rotorisfwithin about '15 either `Iside -of the'verticallposition,'-shutters 53- and' '55; areopenand shutters 52' and 54-closed wheni'the'rotorl-is within about 152 either side of horizontal;Aand `a-ll-shuttersl are open when the rotor `is'within about1f15`eitherside'of an angular position'intermediate-vertical and horizontal. Forall otherl positionsloff" the `rotor 'the-shutters are inf thepro'cessbf'openingorf-closing.

fS-ituated behind disc 41- and the-shuttersis a circular fr'efiector-assembly 69 divided -into'-four quadrants by vertical :light barrier 5I and horifrontal" light v barrierl 522 "f Small *light bulbs 634-111are -i-positionedf within' these quadra-nts;- two` to each* quadrant."When Jvthe two phase voltages inwaveindicatoi' 2 has"the-'=valuesshown-'oppo-y site indicator lights-8U" (Figs: l-'and 2)L thecurrentin-thephase |-windingfof-the mot-or is at ar maximum" `and ythatyinthe phase- 2` winding is zero; For this conditiontheA total`flux-'of'tl'iey revolving `field is generated. bythe -phase y|V windingand-passes througfhsalient polesY 4|' andv 43. To 'illustrate thisfconditi'onf shutters* 52'v and -5'4 are open.' vsh-i-itters-15 3'*- and`55` l closed; and"Y lights 63 through-1Ui'fenei'gized so tha-tflight,`passes through the perforationsf' inl vstrips 48-and;50 and' throughthe perforationsfin bothJ the Y right-i and leftfjperforated semicirclesofd-iscv 4-1 representing the statorl'c'ore. Assuming the'phase wind'-ing tobe ini such` a "direction-as to make pole l 4| a south pole' andpole '543 ua north pole; -therotor will nowbe in=-a= vertical' positionwiththe; "N pcl'e directly under sali-'ent'v polel 4 Forty-fiveelectrical degrees later the -twovolte ages have the value show-nopposite the Bf-S indicator 'lightifl'igs 1E and' 2.!! For thiscondition the current in the phase windingv isreduced and: theicurrentin' the Vphase 2 winding increasedA until the two areequafysoithateoalTluxesaref S produced by'eae'h of thewridin'gs;"rbiilustr'ate this condition all's'hutters are opened ybut'o'nlylight's'65, 66, 69 and 1U are'energized so 'that lightv passes throughthe uppervleft and lower right quadrants of the circularL perforationsin disc 41 and through the left half of perforated strip 48, the upperhalf of perforated strip the lowerA half of perforated strip 49 and theright. half of perforated strip 50. For this condition poles 4| and 42have south polarity and poles.43 and 444 north polarity, and theresultant field is rotated 45 clockwise from its preceding verticalposition. To agree with the newposition of the. eld the rotor islikewise rotated rclockwise 45 from its preceding position. The actionof barriers;

6| and 62 prevents complete illumination of thev perforated strips,which serves to indicate a smaller value of flux produced by the twowind-` ings for this condition as compared with theflux produced by thephase winding in the .preceding condition in which the current in thiswinding had its maximum value.

Forty-five electrical degrees later, as may be seen opposite theindicator light Ill-IU' inFigs. l and 2, the current in the phase 2winding has its maximum value and that in thephase I winding is zero. Toillustrate this condition the shutters 53 and 55 are open, `shutters 52and 53 closed and lights 63 through. 10 energized. For this. conditionthe resultant neld is in line. with poles 42 and 44 as isindicatedbylight passing through the perforations of strips 49 and 5|and the upper and lower semicircles .of perforations in disc 41. Therotor is likewise advanced 45 more, by the rotation of shaft 46, intoalignment with the iield between poles 42 and 44..v n

The various flux presentationsproduced by the flux indicator, includingthe three described above, are shown in Fig. 6, which valso shows theaction of the shutters and lights. In this figure white indicates anopenand black a closed shutter. The angular positionlegends indicate theangular positions of the .N pole ofthe rotor as seen in Figs. 1 and 3.The presentations for the 180, 225, 270 and 315 positions are thesame asfor the 0, 45, 90 and 135 positions, respectively. In order toaccentuate the variation in flux density in the salient poles 4|, 42,43fandf44, reectors 1|, 12, 13 and 14 containingsmalllamps 1I', 12', 13and 14 (the first three-Lnot shown) are positioned on the outside. ofreflector assembly 60 opposite each of the salient poles and designed.to direct light into the edge of. stator 40 directly opposite thepoles. Means, to be described in connection withFig. 5 areprovided toeifect maximum brightness in lamps 1| and13 and minimum brightness inlamps .12 and14f when the rotor is in a vertical position, maximumbrightness in lamps 12 and 14' andminimum brightness in lamps 1| and.13vwhen the` rotor is in its horizontal position, and equal but less thanmaximum brightness in all lamps when the rotor is in a diagonalpositionintermediate .the vertical and horizontal positions. Thetransition from full to minimum brightness is uniform and gives theappearance of a varying ilux density in the poles as the rotorrevolves.1

The transparent areas .8" through I5, backed by lights 8 through |5"'(the latter three not shown), are positioned at 45 intervals about theflux indicator 2 and serve as rotor position indicators, each giving amomentary indication of the angular position ofthe -Nv pole `of therotor as lthe rotor revolves. Theselightsf are connected in parallelWith lights 3 through l5 respectively,

and .in.cooperationtherewith servegto correlate theangular position ofthe 'rotorwith theampll-r tudes and polarities of the two phases .4 and5- asfportray'ed bythe phase indicator 2. i

' The method of driving the various moving parts ofthe demonstratontthedetails vof commutator 33, and 'the 'wiring .diagramare'shown in Fig. 5.Ther'otor'45ismounted on'shaft 46 which is coupled: .to-shaft 32 bymeansyof a flexible coupling 85. Cylinder 3| and the rotating parts ofcommutator 33 (Fig. 2) are mounted on shaft 32. Both'shafts 32 and 46are driven by motor 86 through' worm 81 and gear 88y to rotate rotor 45andthe revolving parts of the. commutatorin a clockwise direction asseen in Fig. 5.x The speed at which the demonstrator operates maybecontrolled 'by motors'peed controller `89. The' demonstrator `may alsobe operated by hand by deenergizingv the motor and pushing crank 90 in-`ward to' engage gears 9| and`92.` f,

The belt 21 (Fig. 2) is so mounted on cylinder 3|4 that rwhen .the Npole fof the rotor points to one ofthe rotor position indicator lightssuch, for example, as light |0" a dividing line be,- tween opaquea'ndclear'sections of the belt is opposite the "cor-responding phaseindicator light 110'..4 a

The commutator 33 comprises a stationary disc of insulating material 80having eight contacts about 10 in lengthfandspaced at 45 intervals aboutthe circumference of a circle. Shaft 32 passesthrough stationary discvand is grounded. by ring 82 andv contact 83.v Revolving contact 8|vismounted on shaft 32 and acts'toground'the contacts on'disc 80 insuccession as the shaft rotates. Lamps 8 and 8' are connected inparallel between the ungrounded terminal of the secondary vwinding oftransformer 84,' the primary of which is connected to a source of A. C.power,`and the 0 contact on disc 80. Similarly parallel connected lamps9-9 through |5'| 5" are connected between the ungrounded terminal of thetransformer secondary and the remaining contacts respectively inaclockwise direction. Lamp 6 is connected in parallel with lamp 8 sinceboth lamps represent similar points on waves 4 and 5. With thisarrangement, as shafts 32 and 46 rotate, the rotor position indicatorlamps 8 through I5 and phase indicator lamp 8" through |5" aresuccessively energized to indicate the point on the cycle of thetwophase voltage corresponding to the position of the N pole of therotor.

The switching of lamps 63 through 10 to produce the 'results alreadydescribed in connection with Figs. 3 and 6 is accomplished by the disc93 and associated contacts of commutator 33. The disc 93 is made ofinsulating material and is mounted on shaft 32 so that it rotatestherewith. The disc carries six conducting contact strips extendingabout 15 in either direction from the 0, 90, 135, 180, 270 and 315points on the circumference of a circle centered on the center of thedisc. Each of these contact strips is conductively connected to thegrounded shaft 32. Two stationary contacts 94 and 95, having a spacedrelationship, are arranged to engage the contact strips of disc 93 andare so positioned that contact 94 is in the center of the 0 contactstrip when the N pole of rotor 45 is directly vertical, or under salientpole 4|. With this arrangement all lamps are energized when rotor 45 is'Within 15 of its vertical or horizontal position, lamps 65, 66, 69 and1 0 are energized when the rotor is within 15 of its 15-225 position,and

aalsme- 7. lampsl, 1,. &1:sandi68rare3energized when the;rotmnlisrwitliinf. cf: its "18593159 position,

required.

The brightnesssroitnx'-intensity lights-:1122, 12"., 13: andi 111:" is:controlled by; Ivariable resistance devic'ef 95; :which comprises;resistance` element 91- andi slidingaacontact:zgfmovablerover the lengthorf themresistancefelement; by '-cranki 99 andi conungrounded terminalof.: the' secondary Vwinding o-ftransformer: v84; while lamps 1'|2" and14' are connected parallel fbetv/eenv fthe; leftl hand :ter-

ofsvresistor 91 and ground', and. lamps; TI andiu'f'are' connectedbetween the right? -hand iemninaland ground.k With :this .arrangementlamps: lzdf'fhaverfullibrightness andi lamps II lz'anlf'have:minimumubrightness when slider Sails "in itsex'treme;4 lleftrlhandposition, as shown imlEig. 51. Rotation. off crank v995 through '90moves slider 98 tolthezcenter'f'of resistorSTresultinf'eqnalllbuti lessthan full' brightness lin all fonrzflamps.. Rotation. ofcrank 99;through; an additional'` 90? lrejvr-rrsesthe; yiirst condition. andproduces tullbrightnessin lamps H and 'lf3' withniinimiimtibrightnessf'in lamps 1'2' and 14. Since eachciamp mus'trchange fromV full to minimum brightness in 90 of rotation of rotor 45thefcrank 9.8i rrr-usty =revolveat. twice the. speed of shaft 46.Thisspeedf increase isaprovided-'fby gears- I0 I- and m21. which `have ia -ratio-of 2:: l.

Withreference toither commutator of Ii?ig...f5 and fthe:camrshown--i-nxrig; f4; (the angularl extent off thecontacts- :andi camsurfaces given `in` the specificr embodiments described .are` notcritical values but merel-y representative `of asatisfa'ctoryidesign.

What :I---clainr is:

if.. Atraining; apparatus for demonstrating the.operationfoffasynchronous motor'. comprising., a waveiillustratingdevicewandI a' flux: illustrating device; fsaid Wave 'illustratingdevice comprising, .a panelrofopaque material; a lZero axis onfsaidpanel equal@ fin length 'toy oneV Wavelength 'fof the: poly.-plfasefvoltagesg orcurrents. tobe fillustratedf-and Eormedbfy'rend'eringvsaid`-=pane1 *transparentaiong saidraxis-fsaid;panelr r'aflscbeingLrenderedtransaparentw-along; the outlinesw'of one l:corniplete:cycleofieachfio :aI plurality-of waves ot thetsa'me frequenc'y, but:different: phases andcoextensive 'with saidi-zeroaxis-ftofrepresent thepolyp'has'e lcurrents or. voltagesfto zber illustrated; a light source.located behindn saidgpanel: and; arranged'. to'fillum'i.- nate the areaof said panelsincludingisaiduvaves; anzend'less belt :supported'beim/'eenV rotatablercylindersfxand interposedi betvfeenfsaid: light..source andi said panel; ssa'idibeltehaving alternate yopaque andtransparent sectionsl equal. i-nzength to.--one Wavelength. ofi 'saidwavesY and: having.' suicient aneaaftoz; cover: thee area; of said.panel 'containing sai'drwaves; means or "driving fone. of .saidcyli-n-,

derstand; meanse for preventing slippagefbetween said(l beltv 'andsaidAdriven c'y1inder said? .linx il'- lustrating: device, comprising a-'stator yelement made of fa.' transparent material and' having-,an outerring-,portion anda: plurality of poles extending; radiallyf fromV `saidring` portion` toward itsscenter: whereby .said stator: element'conforms ta` 'thei'cross-Secti-on perpendicular: "to: the' `sliafftoiga:'synchronousimotorY armature 'core-of the salientpole type,`arrotcrrelernerrtmatle:of aftransparenti;v material andwshapedtoconformto the' iii) crossgsection -perpendicularfto-the shaftfof asynfpositionedfbehind.- said stator-and rotor elements;sa'idwdiscibeing;perforated..beneath saidstator elementandbeneaththepoles of rotor element when aligned-:with the; poles'of-said stator element, individually;controllableelectrically energizedlight souncesjdesigned-to illuminate -fromlthe'rear each oirtheseotoraleareasof` said discV bounded by the center: lines.. of: adjacentstator poles, shutter meanswlocated'between@said' light sources and theperfo-ratio'nsf.'ofl said.l disc.- under. said stator and rotarpolesiiw:controlling the passage of light throughthese perforations', andseparate means operated 'by saidv rotor revolvingI means forcontrolling-- 'saidvshutters and .the energization of saidiligl'itsourceslsofas to introduce light through the perforations. ofi saidrdisc into-said transparent statoriandfrotor elementsin a patterndetermined by,- fthe angular positioniof said: rotor element andconforming-L' to. the magnetic flux' distribution inthe:armature'andield'` cores of asimilar synchronnusmotorxforzfasimi'la'n position of its rotor, and fixed coupling meansbetween 'said' rotor revolvingmeans y 'and said` cylinder driving meanswhereby the said? Wave.:illustratingA device always showsitheamplitudesfand'polarities of the said wavesnecessar'y; toproduce theflux distribution shovvneby theisaid' .ux .illustrating device.

.'2..;Apparatusas; claimed in claim 1 in which additional electricallyenergizedv light sources arranged'l to. introduce :lightfntof the edgeof said statorselement-oppositeeachstator pole are providedland .meansoperated from said rotor revo'lvingzrmeans.:forrcontrolling theenergization of saidfadditionalzlight sources to control theintensitwof.: each; additionall light source in an inverserelationship.ft'ortheV angular displacement of theassociatiedirstatorzpole and the nearest rotor pole...A

3. .Apparatus asi claimed; im claim 2in which a plwralityfof rotorpositions-indicator electric vli-ghts are..spa'cedatregutar intervals`around said ux illustratingdeviceiandiasimilar numbero corresponding:wave position indicatorr electric lights are distributedrat'equa-l1'intervalsubeneath the i1- lustrated'wayes .inzsaid wave'.illustrating device, meansconnecting corresponding pairs of lightsinithelftwagroups inpar-al'lell and switching :meansoperateiby'rsaid.rotorirevolvingi means for' suc'- c'essivel'y,energizingxfsaidpairs of lights asy the rotorlrevolves..

`4L-AT device; tor; demonstrating.` the operation ofi-ia, s'y-nchnmous;Imotor.; said; ldevice comprising ass'tator` 'element.imader of.vaftransparent material and havingani outer'ringap'ortion and a'.plurality of .p'ol'es-iextendingtradially'from said ring'porticnftowa'rd rtslcenter Wherebysaidstator lelement confbr-ms' l'tothe. fcrossr-section perpendicular to thef 'shaft'.sofrfaisymnhronousmotor 4armature "core ofthefsal'ien'tlpole tiype, a rotorelement made ofaatramspareni'materialsand!shaped toY conform to thecrossssection:perpendicular'tothe shaft of a synchronouswmotor neldlcoreof. the salient vpole type; means 'forrrevol'vingjsaidl rotor elementrela'- tiveftofsaid stator element@ a. disc-"of opaquematerialfpositionedlbehind-saidstatorand rotor elementasaid rdiscbeingperforated-beneath said stator element andbeneath thei poles 'ofsaidirotor element when'alignedvvith the Apoles ofi said 'statorelementgxlndividually controllable electrically energized slightAsources :designed to illuminate from the` reani'eachfoffthefsectoralareasoi said disc bounded: by-ft-he 'center-.lines of adjacent statorpoles;y shutter mea-ns' yloca-ted"between said lightsources.and-theperforations of said -disc under said-stator zuicbretcrlpoles for vcontrolling'tl'ie pas-1 sage of light through theseperforations, and separate means operated by said rotor revolving meansfor controlling said shutters and the energization of said light sourcesso as to introduce light through the perforations of said disc into saidtransparent stator and rotor elements in a pattern determined by theangular position of said rotor element and conforming to the magneticflux distribution in the armature and field cores of a similarsynchronous motor for a similar position of its rotor.

5. Apparatus as claimed in claim 4 in which additional electricallyenergized light sources arranged to introduce light into the edge ofsaid stator element opposite each stator pole are pro- 15 vided, andmeans operated from said rotor revolving means for controlling theenergization of said additional light sources to control the intensityof each additional light source in an inverse relationship to theangular displacement of the associated stator pole and the nearest rotorpole.

HARRY M. TUCKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,203,594 Daugherty June 4, 19402,236,217 Manuel Mar. 25, 1941 FOREIGN PATENTS Number Country Date587,544 Germany Nov. 4, 1935 328,010 Great Britain Apr. 16, 1930

